Culture change

03 December, 2010
Developments in processing mean that yeasts are increasingly being tailored to the needs of individual products. Andrew Williams reports
Page 26 

Poor old yeast forever playing third fiddle to salt and flour, which consistently grab all the news headlines. But the times they are a-changin' as some of the most fundamental processes of breadmaking come into question.

For the past 30 years, the main developments in dough conditioning have been the discovery of new enzymes, since hemicellulase first reared its head in 1980. Thus far, it has not been necessary to declare enzymes on the ingredients list. But the concern buzzing around the baking industry is that enzymes will eventually have to be declared, based on murmurings in Europe around food labelling regulations.

The debate is over whether labels would have to include 'enzymes' as a genericingredient, or the full biochemical name, in which case the ingredients list would look like an absolute nightmare to suspicious consumers. If brands think this will impact the perception of products, then this could lead to a fundamental review of processes, which would mean taking a fresh look at the role of yeast.

"For the future, and this is a personal opinion, I think bakers will have to go back to a blank piece of paper and start thinking again about the processes they use to make their product," says Dr Mike Chell, managing director of Lallemand UK. "Yeast is not a substitute for enzymes. But if different processing regimes are considered, then yeast can play a critical role there, because of the behaviour of the yeast in the process. As the process is changed, it will become more and more important to tailor the yeast to the process."

In fact, the shift away from high-speed processes is well under way for speciality breads, with a number of sizeable UK bakery manufacturers investing in sponge and dough processing. Such processes are an ideal vehicle for using different forms of yeast. That means high-activity yeasts for faster processes and medium-activity for longer fermentation. If a baker is looking to make Continental-style products or a different form of fermentation profile, then yeasts are available to suit those requirements.

"I don't think the one-size-fits-all approach is going to be appropriate in the market going forward," says Tom McGibbons, general manager of Mauri Yeast. "We are listening to our customers and we have developments in the pipeline for the new year. There are different needs, such as for high sugar-tolerant products for high sugar and spiced doughs, and we will be meeting that need."

Similarly, DCL Yeast will soon be launching new and "significantly improved" yeasts. "We have strain development programmes and will be launching some of these innovations in the new year," says Mike Abraham, sales manager at DCL Yeast, part of the Lesaffre Group. "The UK uses probably the highest activity yeast in the world. Because we have very fast breadmaking processes, we want a lot of gas in a short time, and the yeasts are geared to do that. Bakers are increasingly aware that there are other yeasts available that work in niche products or long fermentation processes. If you're proving for three hours, you wouldn't recommend a high activity yeast."

Yeast fermentation flavour has been an overlooked area in bakery, but the industry is starting to move away from the perception that yeast is a commodity ingredient. As yeast produces carbon dioxide in the dough, it metabolises the sugars present. In so doing, it produces a spectrum of intermediate metabolites, many of which are precursors for flavour. "If you can ring the changes on that spectrum of precursors, then you can really ring the changes on the flavour profile of bread," says Chell. "Most buyers regard yeasts from all the suppliers to be interchangeable. The one thing that standard UK bread has totally lost is typical fermentation flavour, which is a direct result of going to no-time dough processing. So we're scouring our portfolio and coming up with some very interesting yeast strains, which do give excellent and, more importantly, variable flavour profiling in bread. We have literally thousands of strains of yeast from baking to brewing to wine-making to savoury flavour production which we believe can be applied into baking to give more interesting results."

Yeast is also being developed to deliver key nutrients, such as selenium, especially as the UK moves away from North American wheat to European wheat. One obstacle to development has been the Food Standards Agency, which has thus far thwarted health claims for vitamin-enriched yeasts in the UK, in contrast to other EU countries.

Another major trend in yeast is the shift towards liquid or cream yeast. This is produced in the same way as block yeast, but with water left in to give it a creamy consistency. This offers benefits for hygiene, dosage and control, with no packaging waste. Capital expenditure on a cream yeast system can be upwards of £100,000, which would only be justified if you were taking four to five-plus tonnes of yeast a week. Now, systems are also available for the smaller craft operator too.

While nearly all the large industrials are using liquid, the smaller industrial/large craft are moving towards returnable tank systems. This has been taken up rapidly in the Benelux countries, and the UK is following suit. "It takes yeast contamination out of bakeries. If people walk around with yeast on their hands, it goes on the door handles, it goes everywhere," says Abraham. "The future will see more innovations in liquid handling. It has been taken up widely across Europe."

The firm has been finding success with a product called Kastalia (a bag-in-box concept suitable for craft bakers), and can supply stabilised cream yeast to any bakery using upwards of 50kg of yeast a week in mini bulk containers. It's available in the typical UK high active form, but also in a more European-style medium activity for longer fermentations, flavour development and some high stress processes, because the yeast is more tolerant and resilient. Lallemand has also reintroduced stabilised cream yeast recently. 'Stabilised' means it doesn't have to be constantly stirred, which suits the smaller industrial or large craft baker that cannot justify the expense of a sophisticated cream yeast tank system.

On the volume side of the industry, the systems are becoming ever more sophisticated. "The cleaning, hygiene, dosing, weights and measures side have been brought up to state-of-the art systems now, and the risk of the manual side has been taken away," explains Eddie Ralph of liquid yeast systems supplier Process and Vessels. "They check themselves, there's automatic cleaning and the right temperatures are recorded. If you add the yeast or levain ingredients alongside the water that has been added into the batch, you get a very good consistency every time. With block yeast, it depends how it crumbles and how it's introduced into the mix as to how well it spreads itself across the blend."

The firm is considering introducing a smaller system that is self-contained and refrigerated that can lend itself to both cream yeast and levain starters.


Liquid yeast handling systems

Liquid yeast or cream yeast is now a commonplace ingredient in modern plant bakeries and extends from the large bulk systems down to smaller batching/storage 500kg to 1 tonne containers and, increasingly, in sizes suitable for small craft bakeries. The most common liquid yeasts that are available for the baking industry are comprised of water (approximately 82%) and vegetable matter, that is the yeast itself. It has a consistency not unlike that of a pourable dairy cream.
There are two basic technical requirements for storing liquid yeast: the first is to keep it cool, and that generally means maintaining its holding temperature at between 2-4C; the second is to maintain a homogenous solution that is, to ensure that the yeast cells do not begin to settle under the effects of gravity on the bottom of the storage container, a problem that is overcome by using stabilised cream yeasts.
Yeast is a culture and, as such, it not only requires to be kept cool and gently agitated, but the environment that it is stored and used within, must be kept clean. Clean-in-place systems are increasingly built into the design. Advanced systems can supply the necessary data to the bakery quality system for logging cleaning times and dates.





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